It is estimated that 50% to 90% of pregnant women experience morning sickness or a more severe condition, hyperemesis gravidarum, in which women vomit several times a day.   Morning sickness typically will start between the 4th and 6th weeks of pregnancy, and should typically subside by the 14th or 16th week. 

While it is said that morning sickness is a sign of a healthy pregnancy, the lack of it does not mean that there is anything wrong with your baby or pregnancy.  Some research shows a correlation between lack of morning sickness and a higher incidence of miscarriage, but there is also just as much research indicating that the correlation is not there.

There are many factors that can contribute to causing morning sickness.  Some causes may be:

–  rapid hormone changes.

–  a tricky stomach.  That is, your gastrointestinal tract may be particularly sensitive.

–  enhanced sense of smell and sensitivity to odors.

Other theories about the causes of morning sickness have included a lack of vitamin B6, or a psychological reaction to the stress of having become pregnant.  Few studies have conclusively shown either of these to be true or untrue.

When does morning sickness normally start and what causes it?